1. Field of the Invention
The present invention relates to a semiconductor device socket used for testing a semiconductor device.
2. Description of the Related Art
Semiconductor devices are subjected to various tests prior to being mounted to electronic equipment or others so that latent defects thereof are found and removed. The tests are carried out in a non-destructive manner by the application of voltage stress, the operation and storage under a high temperature condition in correspondence to the thermal/mechanical environmental tests.
The semiconductor device socket used for such tests is generally called as an IC socket which, as shown in Japanese Patent No. 3059946 and also in FIG. 7, is mounted onto a printed circuit board 2 having an input/output section for supplying a predetermined test voltage to the semiconductor device to be tested and transmitting abnormal signals representing the short-circuit or others from the semiconductor device as an object being tested.
The semiconductor device socket fixed on the printed circuit board 2, includes a socket body 4 having an accommodation portion 4a for accommodating a contact-moving member 8 described later to be movable relative to a pair of movable contact portions of a contact terminal 16ai (i=1 to n, n is a positive integer), a guide member 10 having an accommodation portion 10a, in which is mounted a semiconductor device such as a semiconductor element 6 of a BGA (ball grid array) type (see FIG. 8A), for guiding the semiconductor element 6 to the accommodation portion 10a and positioning the semiconductor element 6 relative to the contact terminal 16ai, a contact-moving member 8 disposed in the socket body 4 to be reciprocatable in a predetermined direction, for moving one movable contact portion 16M of the contact terminal 16ai close to or apart from the other movable contact portion 16F described later, and a cover member 12 for transmitting an applied operating force to the contact-moving member 8 as a driving force via a drive mechanism (not shown) of the contact-moving member 8.
At a predetermined position on the printed circuit board 2, there are a group of electrodes electrically connected to the input/output section via conductor layers. As shown in FIG. 7, proximal end terminals 16B of the plurality of contact terminals 16ai provided in the socket body 4 disposed on the printed circuit board 2 are connected to the group of electrodes.
The socket body 4 has the accommodation portion 4a, from which are projected outward the movable contact portions 16M and 16F of the plurality of contact terminals 16ai. 
The respective contact terminal 16ai includes a proximal terminal 16B provided in the socket body 4 in correspondence to each of electrodes 6a of the semiconductor element 6 to mounted, and the pair of movable contact portions 16F and 16M coupled to the terminal 16B and selectively nipping the respective electrode 6a of the semiconductor element 6 to have the electric connection thereto. As shown in FIGS. 8A and 8C, in accordance with the movement of the contact-moving member 8, the pair of movable contact portions 16F and 16M are close to each other to nip the respective electrode 6a of the semiconductor element 6 or away from each other to release an electrode 6a from the nip.
The contact-moving member 8 fixing the guide member 10 to the upper portion thereof while inhibiting the relative movement of a bottom of the guide member 10 is disposed in the accommodation portion 4a of the socket body 4 to be movable in the moving direction of the movable contact portions 16M and 16F of the respective contact terminal 16ai. 
The contact-moving member 8 has openings in the interior thereof, through each of which project outward the movable contact portions 16M and 16F of the respective contact terminal 16ai. The respective openings in the same row are separated from those in the adjacent different rows by partitioning walls (not shown).
In the contact-moving member 8, between the adjacent openings in the same row from which the movable contact portions 16M and 16F of the respective contact terminal 16ai are projected, there is a movable contact presser portion 8P formed to separate the movable contact portion 16M and the movable contact portion 16F. Further, there is a biasing member not shown between one end of the contact-moving member 8 and the inner circumference of the accommodation portion 4a of the socket body 4, for biasing the contact-moving member 8 to an initial position shown in FIGS. 7 and 8C. At the initial position, one of end surfaces of the contact-moving member 8 is brought into close contact with the inner circumference of the accommodation portion 4a of the socket body 4 without any gap.
Further, the contact-moving member 8 is coupled to a drive mechanism comprised of a lever and a pin as shown in Japanese Patent No. 3059946. One end of the lever of the drive mechanism touches to an end portion of the cover member 12.
Thereby, when the contact-moving member 8 is made to move against a biasing force of biasing means in the direction shown by an arrow M in FIG. 8A as the cover member 12 descends in the direction shown by an arrow D in FIG. 8A, the movable contact presser portion 8P moves to separate the movable contact portion 16M of the respective contact terminal 16ai from the movable contact portion 16F. On the other hand, in accordance with the upward movement of the cover member 12 as shown in FIG. 8B, the contact-moving member 8 moves in the direction opposite to that indicated by an arrow M in FIG. 8A by the biasing force of the biasing means and the recovery force of the movable contact portion 16M.
As shown in FIG. 7, the guide member 10 has, in a central portion thereof, the accommodation portion 10a for detachably mounting the semiconductor element 6 therein. The inner circumference of the accommodation portion 10a is formed of a flat surface opposed to the respective end surfaces of the semiconductor element 6 of a square shape, an inclined surface coupling the flat surface to an upper end surface, and a bottom surface intersecting the flat surface. A dimension of the inner circumference of the accommodation portion 10a is larger than the outer dimension of the semiconductor element 6 to be mounted therein with a predetermined tolerance. That is, as shown in FIGS. 8A and 8C, when the contact-moving member 8 maximally moves, a value of a gap C between the respective end surface of the semiconductor element 6 and the flat surface of the guide member 10 is determined to be smaller than the difference (A−B) between the maximum displacement amount A of the movable contact presser portion 8P from the position shown in FIG. 7 to the position shown in FIG. 8A (the displacement amount of the contact-moving member 8) and the maximum displacement amount B of the respective electrode 6a of the semiconductor element 6 following the former (the displacement amount of the semiconductor element 6); i.e., C<A−B. In this regard, the maximum displacement amount B is smaller than the maximum displacement amount A.
The cover member 12 is provided with an opening 12a in the interior thereof to encircle the guide member 10. The cover member 12 is supported by the socket body 4 to be movable upward and downward relative to the socket body 4.
According to such a structure, when the semiconductor element 6 held by a hand of a conveyor robot not shown is mounted to the accommodation portion 10a of the guide member 10 through the opening 12a, the cover member 12 is initially made to descend to the lowermost position shown in FIG. 8A by a presser portion of the conveyor robot and simultaneously therewith, the semiconductor element 6 is lowered. Thereby, as shown in FIG. 8A, the contact-moving member 8 is displaced against the biasing force of the biasing means.
Then, as shown in FIG. 9A in an enlarged manner, in a state that the movable contact presser portion 8P is displaced to move the movable contact portion 16M of the respective contact terminal 16ai away from the movable contact portion 16F and held there, the semiconductor element 6 is placed in the accommodation portion 10a of the guide member 10, whereby the electrode 6a of the semiconductor element 6 is positioned between the movable contact portions 16M and 16F of the respective contact terminal 16ai. 
When the cover member 12 rises as shown in FIG. 8B in a state that the respective electrode 6a of the semiconductor element 6is positioned between the movable contact portions 16M and 16F of the contact terminal 16ai, the contact-moving member 8 is displaced to the initial position by the biasing force of the biasing means and the recovery force of the movable contact portion 16M, and the movable contact presser portion 8P is away from the movable contact portion 16M to be brought into contact with the movable contact portion 16F.
Accordingly, as shown in FIGS. 8B and 9B, the electrode 6a of the semiconductor element 6 is nipped by the movable contact portions 16M and 16F of the contact terminal 16ai, and thus the electrode 6a of the semiconductor element 6 is electrically connected to the contact terminal 16ai. 
In such a semiconductor device socket, as shown in FIG. 8B, when the cover member 12 rises and the contact-moving member 8 is displaced to the initial position by the biasing force of the biasing means and the recovery force of the movable contact portion 16M, there is a case in that the end surface of the semiconductor element 6 may interfere with the flat surface of the accommodation portion 10a in the guide member 10. That is, as stated above, since the value of gap C is determined to be smaller than the difference (A−B) between the maximum displacement amount A of the movable contact presser portion 8P from the position shown in FIG. 7 to the position shown in FIG. 8A (the displacement amount of the contact-moving member 8) and the maximum displacement amount B of each electrode 6a of the semiconductor element following thereto (the displacement amount of the semiconductor element 6), the interference amount D (=A−B−C) does not become nearly equal to zero, and, in addition, there may be a case wherein the difference between the maximum displacement amounts A and B becomes large in accordance with sizes of the respective electrode 6a of the semiconductor element 6 to be a positive value exceeding zero. This is also caused by a fact that there is a limitation in increase of the value of gap C in view of the requirement for the positioning accuracy.
Also, as shown in FIG. 8C, when the semiconductor element 6 interfering with the flat surface of the accommodation portion 10a is further pressed by the displacement of the guide member 10, there is a risk of a so-called one-side contact wherein the electrode 6a of the semiconductor element 6 is away from the movable contact portion 16M as shown enlargedly in FIG. 8D.
In such a case, the value of gap C between the respective end surface of the semiconductor element 6 and the flat surface of the guide member 10 may be properly determined when the contact-moving member 8 maximally moves. Alternatively, after the contact-moving member 8 returns to the original position, the value of gap C between the respective end surface and the flat surface of the guide member 10 may be properly determined. In the latter case, a center of the guide member 10 may deviate from a center of a group of contact terminals 16ai, whereby a center of the electrode 6a of the semiconductor element 6 is not located between the movable contact portions 16M and 16F and accordingly, it is difficult to mount the semiconductor element 6.
Accordingly, as disclosed in Japanese Patent No. 2904782, a structure is proposed for limiting the amount of the displacement of the guide member to the contact-moving member within a predetermined range by supporting the guide member on the contact-moving member to be movable relative to the latter.